1. Technical Field
The present invention relates to a mask, to a mask forming method, pattern forming method, and to a wiring pattern forming method.
2. Related Art
As a method of forming minute wiring patterns of a semiconductor integrated circuit, for example, a photolithographic treatment has been widely used. In the wiring pattern forming method using the photolithographic treatment, large-scale facilities such as a vacuum device and an exposure device are necessary. In the devices, complicated processes are required to form wiring patterns having predetermined patterns. Furthermore, since efficiency in the use of materials reaches several percents, the materials cannot but be scrapped. As a result, there is a problem that a manufacturing cost is increased.
Meanwhile, there has been proposed a method of forming wiring patterns on the substrate by use of a liquid droplet discharging method of discharging liquid droplets of the liquid material from the liquid discharging head, that is, an ink-jet method. In the ink-jet method, liquid materials (functional liquid) for patterns are directly disposed on the substrate, and then the liquid materials are transformed into wiring patterns by heat treatment or the laser beam irradiation. Therefore, according to the above-mentioned method, since a photolithographic process becomes needless, it is possible to largely simplify a pattern forming process. In addition, since a functional liquid can be directly disposed on the desired region, it is possible to form minute patterns and there is a merit that it is possible to reduce the amount of the function liquid to be used.
When the wiring patterns are formed by means of the ink-jet method, lyophilic regions and lyophobic regions are patterned on the substrate in advance to form the wiring patterns so as to have an accurate line width and then functional liquid is selectively disposed on the lyophilic regions to be wiring pattern regions. As a method of selectively forming the lyophilic regions and the lyophobic regions, the following method has been proposed.
(1) A wiring pattern forming method using an image-formation optical method may be used as the method. In the image-formation optical method, patterning is performed on the substrate by means of surface irradiation of the laser beam. The surface irradiation of the laser beam modulates the amount of light at the mask by combining an image-formation system and the mask. For example, when the patterns are collectively irradiated by use of an excimer laser, grooves are sharply formed on the substrate. Moreover, lyophilicity is increased by the formation of the grooves and the alteration of the grooves caused by the laser irradiation (see JP-A-6-267986).
(2) A wiring pattern forming method using a photo mask may be used as the method. In the method, a mask is formed by patterning grooves corresponding to the wiring patterns on the resistor, and the mask is disposed on the substrate so as to come in contact with the substrate. Then, the laser beam is irradiated on the substrate through the mask to form grooves serving as wiring patterns (see JP-A-11-65124).
(3) A wiring pattern forming method using a metal mask may be used as the method. The metal mask is formed of a metal such as stainless steel, and has openings corresponding to the patterns. In the present method, the laser is irradiated on the metal mask, and then patterns are formed on the substrate by the laser beam transmitted through the openings of the metal mask (see JP-A-2004-134446).
However, the inventions disclosed in the above-mentioned methods have the following problems.
(1) When the wiring patterns are formed on the entire surface of the substrate, the image-formation optical method disclosed in JP-A-6-267986 cannot but increase a diameter of the image-formation system (lens). Therefore, the manufacturing cost is increased. In addition, in the scanning method, the pattern is divided into several sections and then the laser beam is irradiated on the several sections. When the scanning method is employed, high alignment accuracy is required to irradiate the laser beam on the divided patterns.
(2) In the wiring pattern forming method using a photo mask disclosed in JP-A-11-65124, the contact surface between the substrate and the resistor serves as a pattern forming surface. Accordingly, when the mask is repeatedly used, the mask is worn. Furthermore, when the misiles occurs during the irradiation of the laser beam, the misiles are attached to the mask. As a result, the mask is contaminated.
(3) In the wiring pattern forming method using a metal mask disclosed in JP-A-2004-134446, the metal mask is formed by means of a boring machining, which is performed by use of an etching method, a plating method, and a laser machining method. However, since the substrate is thick, it is difficult to minutely form the boring portion and to form patterns with high resolution. Furthermore, the metal mask has stiffness and flatness lower that those of a glass substrate. Accordingly, the metal mask does not come in close contact with the substrate, and does not have excellent resolution. Moreover, since the metal mask is deformed by extraction structure, it is not possible to form the extraction patterns.
(4) In addition, the common problem of the inventions disclosed in JP-A-6-267986, JP-A-11-65124 and JP-A-2004-134446 is that the strength of the contact mask is low due to the through holes corresponding to the wiring patterns on the contact mask.